Understanding the Charges
* Calcium (Ca): Calcium is in group 2 of the periodic table, meaning it has 2 valence electrons. It tends to lose these electrons to achieve a stable octet, forming a +2 cation (Ca²⁺).
* Phosphate (PO₄³⁻): Phosphate is a polyatomic ion consisting of one phosphorus atom and four oxygen atoms. The overall charge of this ion is -3 (PO₄³⁻).
Achieving Electroneutrality
To form a neutral compound, the positive and negative charges must balance. This means we need three calcium ions (Ca²⁺) to neutralize two phosphate ions (PO₄³⁻):
* 3 Ca²⁺ (3 x +2 = +6 charge)
* 2 PO₄³⁻ (2 x -3 = -6 charge)
The Formula
The resulting compound is Ca₃(PO₄)₂, which is called calcium phosphate. The subscript numbers indicate the ratio of ions needed for electroneutrality.
Explanation
* 3 Ca²⁺ provides a total positive charge of +6.
* 2 PO₄³⁻ provides a total negative charge of -6.
* The overall charge is +6 - 6 = 0, which means the compound is neutral.
In Summary
Calcium and phosphate ions combine in a specific ratio (3:2) to form calcium phosphate, Ca₃(PO₄)₂, ensuring that the positive and negative charges balance, resulting in an electrically neutral compound.
